Control system for the contactless scanning of textile webs and like sheet material



Nov. 29, 1960 LEIMER ETAL L) OF TEXTILE W Filed Oct. 1, 1958 FOR THECONTACTLESS SCANNING EBS AND LIKE SHEET MATERIAL 2 Sheets-Sheet 1CONTROL SY Nov. 29, 1960 A. LEIMER ET AL CONTROL SYSTEM FOR THECONTACTLESS SCANNING Filed Oct. 1, 1958 OF TEXTILE WEBS AND LIKE SHEETMATERIAL 2 Sheets-Sheet 2 INVENTORS: ,uararze/ms/e 4 00 N16- 25/915CONTROL SYSTEM FOR THE CONTACTLESS SCANNING OF TEXTILE WEBS AND LIKESHEET MATERIAL Albert Leimer, Beimlerstr. 15, Augsburg, Germany, andLudwig Zerle, Paarstr. .4, Mering, Germany Filed Oct. 1, 1958, Ser. No.764,594

Claims. (Cl. 250-219) The present invention relates, in general, tocontrol systems for travelling sheet material webs and, in particular,to a photoelectric apparatus for the contactless scanning control of theedges of the webs.

It is an object of the present system to provide means offering thepossibility of completely eliminating the sensitivity of a controlsystem to contamination by dirt, difference in photocell aging, a changein the voltage of the light source, etc.

It is another object of the present invention to provide meanspermitting the control of web-edge migrations by the quality of thelight reflected by the web material rather than by light quantum.

It is another object of the present invention to provide means affordinga zone of edge migration in which no control operation is effected.

It is another object of the present invention to provide' meanscontributing to a variation in the width of a zone of edge migration inwhich no control operation is effected.

It is another object of the present invention to provide means renderingit possible to control web-edge migrations through the use of anintermittent light source.

These and other objects of the invention will become further apparentfrom the following detailed description, reference being made to theaccompanying drawings showing preferred embodiments of the invention.

In the drawings, which illustrate the best modes presently contemplatedof carrying out the invention:

Fig. 1 is a more or less diagrammatic and schematic illustration, partlyin section, of an apparatus pursuant to the present invention for usewith sheet material which has an irregular or scattered light reflectioncharacteristic;

Fig. 2 is a top plan view of the apparatus shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 for use with sheet material which hasa uniform or regular light reflection characteristic; and

Fig. 4 is a schematic wiring diagram for the control apparatus shown inFig. 1.

In contrast to prior art devices, which are based upon measurement of aquantum of light or the difference between two light quanta, theapparatus of the present invention utilizes the quality of the lightreflected by the sheet material web to control the path of travel of theedge thereof.

The term light quality as used herein, does not refer to a certainconstant wavelength or color, but to varying light of a preferablydetermined frequency. The present invention deals primarily with lightwhich is varying in intensity, and, under. certain conditions, it dealsalso with light which is varying in frequency. A light source, whichprovides rhythmic light intensity variations, radiates its rays into thespace or area in which photoelectric cells are to control the course orpath of travel of the edge of the sheet material web. This area must befree of all other objects. When a sheet material web enters the StatesPatent scanned area, a portion of the light ray directed thereon by alight source is reflected by the web onto one or more photoelectriccells, depending upon the reflection factor or character of thematerial. The reflection may either be irregular or uniform. The lightsources and photoelectric cells are so arranged and blocked off thatdirect radiation to the photoelectric cells is prevented. Thephotoelectric cells monitor or scan a conical portion of the area infront thereof. In webs formed of a material that provides regularreflection of light, for example in the case of sheet material as clearas glass, the longitudinal axis of the scanned conical area forms anangle with the plane of the web such that a light ray radiated from thelight source to the web is reflected thereby to the photoelectric cell.

Referring now to Figs. 1 and 2 of the drawings in detail, there is showna web-edge control system 60 pursuant to the present invention. A lightsource 1,. here shown as an incandescent lamp, is mounted over a sheetmaterial web which is moving in the direction of the arrow 61. The lightsource is energized by an alternating current voltage supply so that thelight rays vary in intensity in accordance with the frequency of thesupply.

By means of a suitable rectifier 97 the current from the A.-C. sourcecan be interrupted during one half cycle thereof, so as to increase thevariation or flickering of the light rays. The photoelectric cell 4 ismounted above the Web and has a conical field of view 3 through whichthe web is moving in the direction of the arrow 61. By irregular ordiffuse reflection from the upper surface 62 of the web, light rays fromthe lamp 1 are reflected to; the photoelectric cathode 8 of the cell 4.The light is reflected through a passageway 63 defined by an enclosedlight tube or channel 6 provided with an apertured closure plate ordiaphragm 5 having a restricted opening 64 which limits the field ofview 3 of the photocell. The inner surface 65 of the tube 6 is formed ofnon-reflecting light absorbing material so that rays of light whichimpinge thereon, for example the light ray 7 reflected through opening64, do not reach the photoelectric cell 4 which is mounted at the rearend of the tube 6. A second light, tube '10, having a front end aperture65 in front end plate 11 and a photoelectric cell 9 at its rear end, ismounted laterally of tube 6 and is similar in all respects thereto.

In the condition of the parts shown in Fig. 1, there is nothing in thefield of view 12 of the photoelectric cell 9 so that no light isreflected from web 2 through aperture 11 to the cathode 13 of thephotoelectric cell. The photoelectric cells 4 and 9 control lateraladjusting devices, for moving the web or its edge in the direction ofthe arrows 66, through amplifiers and relays, as hereinafter describedin detail. If the response points of these conventional lateraladjusting devices (not illustrated) are set to coincide with the centerlines 14 and 15 of the conical scanning or viewing fields 3 and 12,respectively, of the photoelectric cells 4 and 9, respectively, thedistance or section represented by the arrows 52 between said centerlines represents the range or zone of lateral excursion or migration ofthe web edge 16, within which the edge can move in the direction of thearrows 66 without effecting the energization or operation of a lateraladjusting device. The broken line 17 in Fig. 1 represents a fixedvertical axis between the light tubes 6 and 10. If said tubes aremounted so that they can be adjustably rotated about said axis 17, theresponse points for the lateral adjusting devices, which coincide withthe center lines 14 and 15, respectively, can be moved as close to eachother as desired, i.e. the distance 52 can be reduced, as will bereadily apparent from Fig. 2.

More specifically, viewing Fig. 2, when the cells '4 and 9 are rotatedin a clockwise direction as indicated at M about the axis 17, the centerlines 14 and 15 will each approach the edge 16 in opposite directions soas to W reduce the extent of the range 52.

Referring now to Fig. 3 in detail, there is shown another embodiment ofa control system 67 pursuant to the present invention. In thisembodiment a light source 18, energized from an A.-C. source, radiatesits light rays onto the upper surface 68 of a web 20 which is movingperpendicular to the plane of the drawing, as in Fig. l. The web 20 isformed of material having a very high reflection characteristic so thatthe reflection from surface 68 is uniform and not uneven or irregular asin the case of surface 62 of web 2. For the purpose of simplicity, onlyone photoelectric cell 19 is illustrated. In order to limit the field ofview or conical monitoring area 21 of the photoelectric cell, provisionis made for an optical system comprising a lens 22 and a diaphragm 23interposed between the lens and the photoelectric cell, the diaphragmhaving a central aperture 69. The axis 27 of the optical systemintersects the web 20', at such an angle that a light ray 53 radiatedfrom the source 18 has such an angle of incidence to provide an angle ofemergence which is such that the reflected ray 54 is coincident with theaxis 27.

The lens 22 produces an image of the web 20, within the field of view21, in the plane of the diaphragm 23 at the aperture 69 thereof. Bychanging the diameter of the aperture 69, it is possible to preciselylimit the field of view of the photoelectric cell 19. The baffle orpartition 26 is interposed between lamp 18 and photoelectric cell 19 toprevent light rays from being radiated directly to the photoelectriccathode 24.

1 Referring now to Fig. 4 in detail, there is shown a wiring diagram ofthe control system 60. As previously described, the light source -1 isconnected to an A.-C. source 70 and light rays therefrom impinge uponthe sheet material web 2 from which they are reflected into the lighttubes 6 and through openings 64 and 65 to energize the photoelectriccells 4 and 9. The varying light rays produce A.-C. voltage outputs atthe photoelectric cells. Photocell 4 developes its output signal voltageacross load resistor 28 and photocell 9 developes its output signalvoltage across load resistor 29. The output signal voltage of cell 4 isapplied through a coupling condenser 30 to the control grid 71 of thetriode 32. The output signal voltage of cell 9 is applied throughcoupling capacitor 31 to the control grid 72 of the triode 33.

The signal voltages are amplified in the respective tubes and the tubeoutputs are applied through coupling capacitors 34 and 35 to rectifiernetworks 73 and 74, respectively. Network 73 comprises rectifiers 36 and37 connected in opposition to condenser 34 and condenser 38 in parallelwith rectifier 37. Network 74 comprises rectifiers 39 and 46 connectedin opposition to condenser 35 and condenser 41 in parallel withrectifier 40. It will be noted that each of the tubes 32 and 33 iscathodebiased by a resistor 75 and a bias cell 76. The resistors 77 areconventional grid voltage dropping resistors. The resistors 78 areconventional plate load resistors for the tubes 32 and 33 across whichtheir output voltages are developed. The alternating voltage outputs oftubes 32 and 33 are rectified by their associated rectifier networks 73and 74 and'charge the condensers 38 and 41. The charges on thesecondensers are applied as negative biases to the control grids 79 and 86of the triodes 42 and 43, respectively. The grid resistors for saidtubes are indicated at 81 and 82 connected to the reference potentialline 83. A suitable plate voltage supply for tubes 32 and 33is'connected between terminals 84 and a suitable plate voltage supplyfor tubes 42 and 43 is connected. between terminals 85.

A relay 44, which operates the relay contacts 46 con stitutes the plateload for tube 42 and the relay 45, which operates the relay contacts 47,constitutes the plate load for tube 43. The contact .6 a e n rm y p n athe contacts 47 are normally closed. When contacts 46 are closed a coil48 is connected to a suitable voltage supply which is connected betweenthe terminals 86. When the contacts 47 are closed a coil 49 is connectedto said voltage supply. The coils 48 and 49 operate a conventionalcontact mechanism 50 which may be a reversing relay. A reversing motor51 is energized through the contact mechanism 50 in conventional manner.The motor 51 operates a conventional adjusting mechanism (notillustrated) for moving the web transversely of the direction of arrow61 in Fig. 2.

The control system 60 operates as follows: If the Web 2 is not'in aposition to reflect light to the photoelectric cells, there are nosignals applied to tubes 32 and 33 so that condensers 38 and 41 are notcharged and tubes 42 and 43 are not blocked and remain conductive. As aresult, the relays 44 and 45 are both energized so that the normallyopen contact 46 is closed and the normally closed contact 47 is open. Asa result, coil 48 is energized and operates the reversing relay 50 toenergize the motor 51 for clockwise rotation, as shown by arrow I; Themotor now operates the web-adjusting mechanism so that the web is movedin the direction of arrow 87 As soon as the web has been moved sufli inFig. 1. ciently to reflect light to the photocell 4, the condenser 38 ischarged, tube 42 is cut off and relay 44 is de-energized so that contact46 opens and interrupts the circuit of coil 48 to stop the motor.Thereafter, if the edge 16 migrates sufficiently in the direction ofarrow 87 to reflect light to photocell 9 so that both cells are nowenergized, the condenser 41 is now also charged so that tube 43 is cutoff and relay 45 is de-energized. This causes contact 47 to close tocomplete the circuit for coil 49 and energizes reversing relay 50 toenergize motor 51 for counterclockwise rotation, as shown by arrow II.This energizes the adjusting mechanism to move the web 2 in thedirection of the arrow 88 in Fig. 1. When the web has been moved out ofthe viewing field 12 of cell 9 so that it is only in the viewing field 3of cell 4, as shown in Fig. 1, no light is reflected to cell 9 but lightis still reflected to cell 4. As a result, the tube 43 is renderedconductive again, contact 47 is opened to dc-energize coil 49 andinterrupt the motor.

Various changes and modifications may be made without departing from thespirit and scope of the present invention and it is intended that suchobvious changes and modifications be embraced by the annexed claims.Having thus described the invention, what is claimed asnew and desiredto be secured by Letters Patent, is:

1. A control system for the contactless scanning of sheet material webscomprising'photoelectric means disposed to scan a marginal edge of theWeb and disposed at one side thereof, a source of intermittent lightrays disposed at said one side of the web to shine light thereonforfreflection to said photoelectric means, means to prevent directradiation of light from said source to said photoelectric means, saidphotoelectric means comprising a pair of laterally related photoelectricdevices each having a predetermined field of view, and the axes of saidfields of view defining a predetermined range of migration of themarginal edge of the web within which a lateral web adjustment is notrequired, each photoelectric device being mounted at one end of a lighttube having a light opening at the other end for limiting the associatedfield of view, each tube having a light absorbing inner surface.

2. A control system for the contactless scanning of sheet material webscomprising photoelectric means disposed to scan a marginal edge of theweb and disposed at one side thereof, a source of intermittent lightrays disposed at said one side of the Web to shine light thereon forreflection to said photoelectric means, means to prevent directradiation of light from said source to said photoelectric means, saidphotoelectric means comprising 'a pair of laterally relatedphotoelectric devices each having a predetermined field of view, theaxes of said fields of view defining a predetermined range of migrationof the marginal edge of the Web within which a lateral web adjustment isnot required, and means mounting said photoelectric devices for rotationabout a fixed vertical axis therebetween to vary said predeterminedrange and to adjustably position said light tubes relative to themarginal edge, each photoelectric device being mounted at one end of alight tube having a light opening at the other end for limiting theassociated field of view.

3. A control system for the contactless scanning of sheet material webscomprising photoelectric means disposed to scan a marginal edge of theweb and disposed at one side thereof, a source of intermittent lightrays disposed at said one side of the web to shine light thereon forreflection to said photoelectric means, means to prevent directradiation of light from said source to said photoelectric means, saidphotoelectric means comprising a pair of laterally related photoelectricdevices each having a predetermined field of view, the axes of saidfields of view defining a predetermined range of migration of themarginal edge of the Web Within which a lateral Web adjustment is notrequired, and means mounting said photoelectric devices for rotationabout a single axis to vary said predetermined range, each photoelectricdevice being mounted at one end of a light tube having a light openingat the other end for limiting the associated field of view, saidrange-varying means being means to adjustably position said light tubesrelative to the Web edge.

4. A control system for the contactless scanning of sheet material Webscomprising photoelectric means disposed to scan a marginal edge of theweb and disposed at one side thereof, a source of intermittent lightrays disposed at said one side of the web to shine light thereon forreflection to said photoelectric means, means to prevent directradiation of light from said source to said photoelectric means, saidphotoelectric means comprising a pair of laterally related photoelectricdevices each having a predetermined field of view, the axes of saidfields of view defining a predetermined range of migration of themarginal edge of the web within which a lateral web adjustment is notrequired, means for moving the web in opposite directions laterallythereof, means to energize said moving means for operation in a firstdirection when no light is reflected to both said photoelectric devicesand in an opposite direction when light is refiected to both saidphotoelectric devices, means to deenergize said moving means when lightis reflected to one only of said photoelectric devices, and meansmounting said photoelectric devices for rotation about a fixed verticalaxis therebetween to vary said predetermined range and to adjustablyposition said light tubes relative to the marginal edge, eachphotoelectric device being mounted at one end of a light tube having alight opening at the other end for limiting the associated field ofview.

5. A control system as defined in claim 4, further characterized in thatsaid light source includes means for energizing said light source froman A.-C. source, and a rectifier interposed between said sources.

References Cited in the file of this patent UNITED STATES PATENTS2,196,893 Berry Apr. 9, 1940 2,208,447 Berry July 16, 1940 2,220,736Stockbarger et a1 Nov. 5, 1940 2,246,501 Bradner et a1. June 24, 19412,295,327 Bendz Sept. 8, 1942 2,445,041 Scholz July 13, 1948 2,566,399Bishop Sept. 4, 1951 2,810,316 Snyder Oct. 22, 1957

